1. Field of the Invention
The present invention relates to a transportation system and, more particularly, to a transportation system including an entry unit for a plurality of products, a plurality of cells for performing processing of the entered products, a discharge unit for discharging the products which the predetermined cells have finished processing, and a transport unit for moving the products through the entry unit, cells, and discharge unit, all controlled by a central processing unit (CPU) cooperating with a main memory.
The above transportation system can be used in various fields, for example, equipment for manufacturing and testing printed circuit boards (PCB's). The manufacture and testing of such products (PCB's) require much human labor and demands for automation (unmanned operation) have been rising.
2. Description of the Related Art
There are two leading types of conventional transportation systems:
1) Transportation systems using conveyors
2) Transportation systems using self-propelled carts
In type 1), products are placed on a conveyor and moved in a single direction, during which they are subjected to various types of processing (manufacture and testing).
In type 2), products are placed on self-propelled carts which can move two-dimensionally and are moved to various processing locations.
In the transportation system of type 1) using conveyors), there is the problem that products entered from the entry unit simply move toward the discharge unit in the order of their entry and that flexible processing (manufacture and testing) in accordance with the type of the product is difficult.
In the transportation system of type 2) (using self-propelled carts), when the products involved are of diverse types for short run production, there is a problem that the flow of products becomes complex and control of the transport becomes extremely complicated. Considering these problems in slightly more detail, in the transport of products using self-propelled carts, to raise the efficiency of transport, the practice has been to keep the products in racks or containers specifically designed for the various products and then move them for the predetermined processing. When doing this, in managing the transport of products, it is necessary to manage the large number of racks and containers prepared for the different products produced in small lots, making matters considerably complex. Further, the frequency of transport inevitably increases, so management becomes considerably complicated. Also, as products are processed, defective ones are removed, so the amount of products in the racks or containers gradually change. On-line management of the status of these, therefore, is required at all times.